Height-adjustable table

ABSTRACT

The present invention relates to an improved height-adjustable table (1) which can assist and motivate the user to use the height-adjustable table in a manner which increases health, burning of calories and well-being. The table features a system for determination of user presence and measurement of the time of user presence which can be used for alerting the user to change from a sitting to a standing position in front of the table in intervals based on the practical user presence of the table.

The present invention relates to a height-adjustable table. Height-adjustable tables are also known as sit/stand desks.

A common height-adjustable table comprises a frame to which a table top is mounted. The frame is attached to one end of at least one linear actuator in the form of a lifting column. A foot is mounted to the other end of the lifting column. As examples of these types of lifting columns reference is made to WO/2004/040169 A1 and WO 2009/033486 A1 both LINAK A/S. The electrically driven lifting columns are connected to a control and an operating panel. These units are jointly denominated linear actuator systems.

Although height-adjustable tables comprising a linear actuator system are becoming more widespread, it is a fact that many users do not make use of the most obvious functionality, i.e. the height-adjustment. This contrasts with the known benefits that movement during the day has for health, especially for our metabolism. Standing and moving burns more calories than sitting and engages the leg muscles of the user. In addition to the higher calorie burn when standing it is also proven that standing and moving during the day improves circulation, energy, stress and the overall well-being of the user. Just the act of going from a seated position to a standing position forces the body to work against gravity and helps strengthen our stabilizer muscles. In general, it is recommended that sedentary workers mix sitting and standing during an average workday—sitting or standing for no longer than one hour before changing position. A recommended goal is to strive for an extra 120 minutes of standing during a workday and to change postures at least 8 to 16 times. Further, it has been recognized that the efficiency of the worker is enhanced if a standing position is taken. Alerting systems has been proposed for alerting the user to change from a sitting position to a standing position and vice versa. However, such a system can only be rendered reliable if the user is present in front of the table. The actual monitored time of user presence is needed for calculating and alerting the user to change with regular intervals from a sitting to a standing position. If the user is not present in front of the table, the sit/stand alerting algorithm should register the period and calculate new sit/stand intervals according to pre-programmed user settings.

Additionally, the information on user presence can be utilized to activate stand-by or close down procedures of devices or equipment arranged on or in connection with the desk in order to save energy. Close down could be initiated on event of a timer expiration of a timer which measures the lapsed time of non-user presence at the desk. U.S. Pat. No. 9,486,070B2 to Stirworks Inc., suggests implementing a pressure sensitive mat or a temperature sensor with a sit-stand desk in order to determine user presence and alerting the user recommending the change to a standing position. The system further comprises means to observe if the person is busy having a conversation with another person. In an embodiment, a microphone with voice recognition is used for this purpose. If the person is busy, the alert will be postponed to a later and more convenient time. As such the solution provided solves the problem but a pressure sensitive mat is quite expensive. Implementing a temperature sensor with a sit-stand desk is quite challenging since the person can take position in front of the desk in a variety of ways also including both sitting and standing positions. A low-cost sensor cannot be used, since it only senses heat over a short distance which makes it crucial that it is arranged in close proximity to the user. Even using an expensive IR temperature sensor is a challenge, in terms of where to position the temperature sensor in connection with the desk in order to produce a reliable signal representing user presence status.

Thus, there seems to be an urgent need for providing an alternative solution for sensing user presence at a sit-stand desk as input for various purposes such as e.g. prompting the user to change from a sitting to a standing position or for energy saving purposes closing down power consuming devices when the user is not present. A solution which is more economical and technically not as dependent on close proximity to the user is appreciated.

The objective of the invention is to provide an alternative user presence determination system which in an inexpensive, simple and reliable manner is capable of determining if a user is present at a sit-stand desk. According to the invention, this is achieved by modifying the control to further comprise a system for determining user presence and to use the determined state of user presence as input for determining the lapsed time the user takes a sitting or standing position at the table, and to alert the user to change from a sitting to a standing position or vice versa when preset values for sitting and/or standing in front of the table have lapsed.

More specifically, the invention concerns a height-adjustable table comprising a frame, a table top and a linear electric actuator system for providing a vertical displacement of the table top in relation to the frame, where the linear electric actuator system comprises at least one linear actuator and a control. Further it includes a system for determining the actual height adjustment level of the table providing information to the control and an operating unit with activation keys for user activated height-adjustment of the table, where the operating unit is connected to the control and configured to transmit requests corresponding to the activation of the activation keys. Further, it includes a system for determination of user presence comprising a microcontroller and at least one sensor for picking up signals originating from mechanical vibrations generated by the user and conveyed through the components of the height-adjustable table, the at least one sensor being arranged in its position on one of the components of the height-adjustable table, and where the microcontroller is adapted to sample and record the signal/s obtained by the at least one sensor into a set of data, further filtering the set of data in order to collect signals originating from user presence and suppressing noise signals originating from sources not relating to user presence, integrating the filtered signal over a time interval and determining by comparing to threshold values or data patterns the state of user presence being determined to be one of 1) present at the table or 2) not present at the table, and where the system for user presence further includes an interface for indicating or communicating said state to the control.

It is appreciated that a high pass filter is implemented filtering and suppressing all signals from direct current and upwards until a first cut off frequency. A suitable cut off frequency could be in the range of 0,001 to 10 Hz.

Additionally, a low pass filter is implemented aiming at suppressing high frequency noise signals. A suitable cut off frequency is in the range of 300 to 1000 Hz. In this manner, the cut off frequency can be tailored to suppress noise signals originating from computers, ventilators, power supplies or light sources arranged on or in proximity of the table. Since the filters are implemented using a microcontroller to sample the signals from the sensors and by processing portions of preprogrammed code (software), it will be within the scope of the invention to make it possible for the user to change the cut off frequencies of the filter in order to find the best mode of suppressing specific sources of noise and to highlight the signal of interest supplied from the vibration sensor.

Depending on the measured value of the signal from the sensor, thresholds can be setup correspondingly to a reliable signal indicating user presence or the absence of the user. An automatic setup can be foreseen configuring a learning session for the system, where the user is inactive and a learning session for the system, where the user is active e.g. by typing on a keyboard, moving a mouse, moving papers or touching the table with various parts of the body or items in contact with a component of the height-adjustable table.

Additionally, any user activation of the operation panel or any other user control for height-adjustment of the table as e.g. a software implemented control in the form of an app for the computer should also be accepted as a defined signal of user presence.

In an embodiment, the sensor for picking up signals originating from mechanical vibrations is either a vibration sensor; an acoustic sensor; or an accelerometer. Each sensor has advantages and disadvantages when it comes to how sensitive it is when picking up vibration signals. Bill of materials and easy integration into a height-adjustable table is another issue.

In a further embodiment, the sensor is arranged in its position on one of the components of the height-adjustable table using a non-flexible means that convey the vibrations from the table to the sensor.

Appreciated is an embodiment, where the sensor is arranged in a cavity formed in the table top where the cavity is being adapted to receive and retain the sensor in its position, and where the walls of the cavity are adapted for conveying the mechanical noise to the sensor. As it is explained, picking up the vibration signal requires that the sensor is physically connected to a component of the table, which conveys the vibrations generated by the user presence.

In an embodiment, the acoustic sensor is a microphone capsule. Microphone capsules are very prone to pick up acoustic noises originating from or conveyed through the mechanics. In the field of producing high quality microphones, it is an art to design noise reducing means to cover the microphone capsules and suppress mechanically conveyed noise. This includes rubber or silicone bushings or springs but is not limited hereto. Contrary to that, the normal disadvantage of a microphone capsule is, according to this invention, used in a positive context for determining user presence.

It is in another embodiment appreciated that the microphone capsule is of the type electret microphone featuring a build-in signal amplifier in the form of a FET. A FET arranged close to the microphone pick up is advantageous since the small signal originating from the microphone is amplified, which gives a better signal to noise ratio over electrical noise induced in the cables.

In a special embodiment of the invention, the system comprises two microphone capsules, where the first microphone capsule is arranged connected to a component of the table by means of a non-flexible fixing means, which is non-dampening of mechanical noise, such as e.g. a hard plastic or metal bushing, and where the second microphone capsule is arranged with a mechanical noise dampening means such as e.g. a rubber or silicone bushing, and where the microcontroller samples and records the signals in the time domain and determines a state of user presence, and where the signal from the microphone capsule arranged with a mechanical noise dampening means is used for determining the background noise serving to calibrate the state of user presence accordingly compensating for the background noise.

In yet another embodiment, the sensor is an accelerometer, where the signals from the sensor representing the individual axis are sampled by the microcontroller, and the difference in amplitude from the previously sampled value is calculated, and the difference in measured values from the individual axis is combined to one resulting value corresponding to the incremental measured value of the mechanical vibration induced by the user for that specific sample, and the measured value of the resulting values of samples is integrated over time enhancing the integrity of the value, and the integrated value is compared with a threshold value for determining the state of user presence, the state of user presence being determined to be one of 1) present at the table or 2) not present at the table, and where the system for user presence further includes an interface for indicating or communicating said state of user presence to the control.

In an embodiment, the system for user presence determination is arranged in connection with or in the control in the control box.

In another embodiment, the system for user presence detection is arranged in connection with or in the control panel fixed to a part of the height-adjustable table.

Practically, in an embodiment, the system for user presence detection is arranged as a part of the electronics on a printed circuit board for the control or control panel, or as a piggy back to one of the printed circuit boards or as a separate item having a housing and a printed circuit, and equipped with a cable connection to be connected to the control or the hand control, or as a dongle to be plugged into the control or the hand control.

Further, in an embodiment, the sensor itself is arranged in a separate housing and connected to the control or control panel by a cable, or the sensor is arranged in a dongle, which can be plugged into a port in the control.

In an embodiment, the sensor is arranged outside the control or the control panel, and is supplied with means for fixation of the sensor itself in mechanical connection with a component of the table, such as e.g. the table top, ensuring that the sensor picks up the vibrations generated by the user being present at the table and conveyed through the component of the table.

In order to take advantage of the system for user presence determination, the control or an expansion of the control has means for registering the lapsed time where the state of user presence has confirmed the user to be present at the table and means for alerting the user to change between a sitting and standing position based on predetermined sit/stand intervals. The means for alerting can be a panel associated with the table, such as e.g. a display arranged with the control panel. In the simplest form, it can be a light emitting diode or a buzzer over text displays to sophisticated animated displays.

In an embodiment, the system is configured to ignore short intervals, where user presence cannot be confirmed. More specifically the system features a preset delay, which should lapse before the system changes state from user present to user not present. A measured value of the first delay is practically within the range of 1 to 30 minutes. The delay can be predetermined in the software or be a setting configurable by the distributor of the table or by the end-user.

In an embodiment, the system is configured to alert the user when user presence is confirmed. In brief, the system will not alert and prompt the user to change from a sitting to a standing position or vice versa if it cannot be confirmed that the user is present.

As an additional measure against erroneously detecting a user to be present, the system is in an embodiment configured not to change from the state user present to the state no user present before a preset first delay has been completed. Thus, the change of state will need several samples of signals from a sensor to show that the user is present at the table and not just a few samples of signals that could be originating from an incidental touch by a colleague that passes by or delivers a letter etc. Thus, the system for determination of user presence is in an embodiment configured not to change from the state user not present to the state user present before a preset second delay setting has been completed. A measurement of the second delay is practically within the range of 1 to 30 minutes. The delay can be predetermined in the software or be a setting configurable by the distributor of the table or by the end-user.

An embodiment of the invention will be described more fully below with reference to the accompanying drawing, in which:

FIG. 1 shows a perspective view of a height-adjustable table,

FIG. 2 illustrates a height-adjustable table in a sitting position,

FIG. 3 illustrates the height-adjustable table in a standing position,

FIG. 4 is a schematic diagram of the height-adjustable table,

FIG. 5 is a schematic diagram of the height-adjustable table having a user presence determination system with a microphone,

FIG. 6 shows the same schematic diagram of the height-adjustable table as shown in FIG. 5 but featuring an accelerometer,

FIG. 7 shows the height-adjustable table where the table top is shown transparent,

FIG. 8 shows a recording of a microphone signal,

FIG. 9 shows a recording of an accelerometer signal,

FIG. 10 shows the combined value of the accelerometer signals,

FIG. 11 shows a flow chart diagram for measurement and evaluation of sensor values, and

FIG. 12 shows the state machines algorithm for changing states.

FIG. 1 shows a perspective view of a height-adjustable table 1 comprising a table top 2. At each side of the height-adjustable table 1 a linear actuator in the form of a lifting column 3 is mounted in a carrying frame (not shown) onto which the table top 2 is mounted. The other end of each lifting column 3 comprises a foot 4 on which the height adjustable-table 1 stands. The lifting columns comprise a drive unit (not shown) and two or three mutually telescopically arranged profiles. One profile 5 is stationary fixed to the foot 4 and one profile (not referenced) is stationary fixed to the motor housing. Each lifting column 3 is driven by means of an electric motor, which drives a spindle through a gear. The spindle is furnished with a spindle nut secured to the telescopically movable profile(s). The height-adjustment of the table top is thus performed by the lifting columns 3. The adjustment is achieved by activating the operating panel 6.

FIGS. 2 and 3 illustrate a side view of the height-adjustable table 1 in a sitting position 7 and a standing position 8, respectively. Since the length of the lifting columns 3 can be adjusted, the sitting position 7 and standing position 8 can be set to accommodate the physical characteristics and personal preferences of each individual user of the height-adjustable table 1.

FIG. 4 depicts a schematic view of the height-adjustable table 1 comprising a linear actuator 3, a control 9, a system 10 for determining the actual height adjustment level of the height-adjustable table 1, and an operating panel 6.

The system 10 for determining the actual height adjustment level could be determined by potentiometers or Hall sensors built into the linear actuators 3 or by other detection means such as an optical sensor. The system 10 for determining the actual height adjustment level provides input information about the actual height adjustment level to the control 9.

The operating panel 6 is connected to the control 9 for user activation requesting an adjustment of the height level of the height-adjustable table 1 by supplying the at least one linear actuator 3 from an appropriate source of electrical energy (not shown).

The control 9 comprises a memory 11 for storing at least one height adjustment setting 7,8 referring to a sitting position 7 or a standing position 8.

FIG. 5 shows a system for user presence determination including a user presence controller 14, which has an interface to the control 9. Here, the interface is pictured forming a first communication interface 12 and a second communication interface 13, which serve for data communication between the control 9 and the user presence controller 14. It is foreseen that the user presence controller 14 in an embodiment can be integrated in the control 9 utilizing the same physical microcontroller as utilized by the control 9. However, FIG. 5 shows that the system for user presence determination can be an add-on feature, which can be carried out as an extension of the control 9 connectable to the control constructed as a dongle with or without a cabled connection or as a piggy back board connectable directly on the printed circuit board for the control and thus being encapsulated in the same housing as the control 9. As it appears from FIG. 5, the user presence determination system includes a sensor in the form of a microphone capsule 15, which submits an analog audio signal that reflects the vibrations of the height-adjustable table, when the microphone capsule is secured to one of the components of the table. It is appreciated that the microphone capsule is arranged in a cavity formed in the table top in such a manner that the surrounding sounds do not have direct access to the microphone capsule. This has the advantage that only the vibrations in the table, originating from user presence, are picked up by the microphone capsule, which will also make the user presence determination system more immune to surrounding sounds in the form of talk, which will be dampened by the mass of the table top. The analog signal from the microphone capsule is sampled by an ADC (Analog-digital converter) which transforms the analog signals into the digital domain and forwards the signals to the user presence controller for processing. The sampling rate of the ADC can be low since only low frequent signals are of interest. Any signals in the range of 1000 Hz or more will in normal applications, be possible to cut off. However, specific applications as e.g. recognizing if a ventilator fan is spinning could prescribe that a higher sampling rate is needed.

FIG. 6 shows the same basic principle as shown in FIG. 5, but the microphone capsule 15 has been exchanged to an integrated circuit in the form of an accelerometer, the output of which changes in acceleration in all three geometrical directions (x, y, z plane) directly as digital values. Thus, an ADC is not needed since the accelerometer interfaces the microcontroller for the user presence determination system directly. As with the microphone capsule 15, the accelerometer 16 should be arranged in such a way in connection with the height-adjustable table on one of its components that it picks up vibration signals originating from user presence.

FIG. 7 shows the height-adjustable table where the table top is shown transparent. The user presence determination system is arranged in connection with the control 9 in the same housing or in the same housing as the operating panel 6, but could also be arranged in its own housing (not shown) and secured to one of the components of the height-adjustable table, preferably the table top. As a courtesy, it is understood that the sensor itself can be arranged in close proximity to the user presence determination system or be remotely arranged but interfacing the user presence determination system via a cabled connection (not shown).

FIG. 8 shows a recording of a microphone signal. The microphone is arranged in a fixed connection with the table top. As it appears, the microphone capsule picks up very nicely the vibrations originating from user presence. As it can be seen, normal office trivialities as handling paper, typing on a keyboard or using a computer mouse generates sufficient noise or vibration signals to clearly distinguish from periods where there is no activity. A period without activity can be seen between the events of handling papers and typing on a keyboard.

For the sake of completeness, a similar signal is shown in FIG. 9, but with the difference that the signal origins from an accelerometer 16. The three signals from the accelerometer have been recorded for each axis (x, y, z plane). In a further step, the difference in value to the previous signal for that specific axis has been calculated. In a further step, for which the result is shown in FIG. 10, the three signals corresponding to each of the incremental movements since the last sample are combined into one value which reflects the magnitude of the vibration. The direction is not particularly interesting for this application. Thus, the magnitude of the signal is shown in FIG. 10. As with the microphone capsule, using an accelerometer also makes it possible to clearly distinguish between noise and vibrations originating from a user being present and a silent level.

A flow chart diagram for measurement and evaluation of sensor values is shown in FIG. 11. As a first step, data is sampled by the user determination controller system and stored. Further, the values are evaluated in order to filter out values that appear as spikes or out of boundaries. In a further step, the signal is evaluated and filtered with regard to frequency content in a manner which filters out frequency content below a frequency defined as filter 1 and above a frequency defined as filter 2. The filter values can easily be changed by modifying the values in the software. The filtered signal is in a further step integrated in order to obtain a value, which has integrity over time. A comparator compares the signal with threshold values, which are also defined in the software and are changeable. Depending on the state, presence or non-presence, a threshold value Threshold 1 or Threshold 2 is used to determine if a shift in state should be made from presence to non-presence or vice versa. The state machine is shown in FIG. 12, but is further configured with a timer value in the form of delta time T1 and delta time T2 which serves to allow periods of time of inactivity within a period which can still be considered an active state of presence. The same goes for short intervals of activity within a period of time where the state can still be considered an inactive state of presence. The delta time T1 and T2 can be configured by changing the values in the software.

It is also within the scope of the invention when some of the functionality such as e.g. the comparator, the threshold settings, the delays of state shifting are implemented outside the user presence determination system. This could be implemented in the software being run on the microcontroller for the control or in applications on e.g. a personal computer or smart mobile device which connects to the control 9 via a wired or wireless connection. However, a full system for alerting the user of a height-adjustable table to change between a sitting and a standing position or vice versa could be implemented sharing the same microcontroller, which could be the microcontroller which features the user presence determination system. With the information on acceleration and deceleration changes in the vertical direction originating from height-adjustments of the actuator system and sensed by the accelerometer, the system will be able to determine if the table top has been adjusted to a low or to a high position. Such input can be used for specifying if the next alert will be prompting the user to change from a sitting position to a standing position or vice versa. However, if specific measurements contained in the actuator system corresponding to the actual height-adjustment setting, are needed for specifying if the table top is adjusted to a position, which corresponds to a sitting or standing position, it will be obtainable via an interface for the control 9, and be specified by means of e.g. an incremental position determination system implemented in the actuator system itself. 

1. A height-adjustable table (1) comprising: a frame, a table top and a linear electric actuator system for providing a vertical displacement of the table top relative to the frame, where the linear electric actuator system comprises: at least one linear actuator (3), a control (9), a system for determining the actual height-adjustment level of the table providing information to the control (9), an operating unit (6) with activation keys for user activated height-adjustment of the table, where the operating unit (6) is connected to the control and configured to transmit requests corresponding to the activation of the activation keys; a system for determination of user presence comprising a microcontroller and at least one sensor for picking up signals originating from mechanical vibrations generated by the user and conveyed through the components of the height-adjustable table, the at least one sensor being arranged in its position on one of the components of the height-adjustable table, and where the microcontroller is adapted to sample and record the signals obtained by the at least one sensor into a set of data, further filtering the set of data in order to collect signals originating from user presence, and suppressing noise signals originating from sources not relating to user presence, integrating the filtered signal over a time interval and determining, by comparing to threshold values or data patterns, the state of user presence, being determined to be one of 1) present at the table or 2) not present at the table and where the system for user presence further includes an interface for indicating or communicating said state to the control.
 2. A height-adjustable table according to claim 1, where the sensor for picking up signals originating from mechanical vibrations is either a vibration sensor; an acoustic sensor; or an accelerometer.
 3. A height-adjustable table according to claim 2, where the sensor is arranged in its position on one of the components of the height-adjustable table by means of a non-flexible means which conveys the vibrations from the table to the sensor.
 4. A height-adjustable table according to claim 2, where the sensor is arranged in a cavity formed in the table top, said cavity being adapted for receiving and retaining the sensor in its position, and where the walls of the cavity are adapted for conveying the mechanical noise to the sensor.
 5. A height-adjustable table according to claim 2, where the acoustic sensor is a microphone capsule.
 6. A height-adjustable table according to claim 5, where the system comprises two microphone capsules where the first microphone capsule is arranged connected to a component of the table by means of a non-flexible fixing means, which is non-dampening of mechanical noise, such as a hard plastic or metal bushing, and where the second microphone capsule is arranged with a mechanical noise dampening means such as a rubber or silicone bushing and where the microcontroller samples and records the signals in the time domain and determines a state of user presence, and where the signal from the microphone capsule, arranged with a mechanical noise dampening means, is used for determining the background noise, in order to calibrate the state of user presence accordingly while compensating for the background noise.
 7. A height-adjustable table according to claim 2, where the sensor is an accelerometer and where the signals from the sensor, which represent the individual axis, are sampled by the microcontroller, and the difference in amplitude from the previously sampled value is calculated, and the difference in the measured values from the individual axis is combined into one resulting value, corresponding to the incremental measured value of the mechanical vibration induced by the user for that specific sample, and that the measured value of the resulting values of samples is integrated over time, enhancing the integrity of the value, and that the integrated value is compared with a threshold value for determining the state of user presence, the state of user presence being determined to be one of 1) present at the table or 2) not present at the table, and where the system for user presence further includes an interface for indicating or communicating said state of user presence to the control.
 8. A height-adjustable table according to claim 1, where the sensor is arranged in connection with or in the control, or with the control panel, or in a separate housing, and connected to the control or control panel by a cable, or where the sensor is arranged in a dongle which can be plugged into a port in the control or control panel.
 9. A height-adjustable table according to claim 1, where the sensor is arranged outside the control or the control panel and is equipped with means for fixation of the sensor itself in mechanical connection with a component of the table such as the table top, ensuring that the sensor picks up the vibrations generated by the user being present at the table and conveyed through the component of the table.
 10. A height-adjustable table according to claim 1, where the system has means for registering the lapsed time where the state of user presence has confirmed the user to be present at the table, and means for alerting the user to change between a sitting and standing position based on predetermined sit/stand intervals. 